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We use direct numerical simulations of forced MHD turbulence with a forcing function that produces two different signs of kinetic helicity in the upper and lower parts of the domain. We show that the mean flux of magnetic helicity from the small-scale field between the two parts of the domain can be described by a Fickian diffusion law with a diffusion… (More)

- Francesco Picano, Wim-Paul Breugem, Dhrubaditya Mitra, Luca Brandt
- Physical review letters
- 2013

Shear thickening appears as an increase of the viscosity of a dense suspension with the shear rate, sometimes sudden and violent at high volume fraction. Its origin for noncolloidal suspension with non-negligible inertial effects is still debated. Here we consider a simple shear flow and demonstrate that fluid inertia causes a strong microstructure… (More)

- Prasad Perlekar, Dhrubaditya Mitra, Rahul Pandit
- Physical review letters
- 2006

The existence of drag reduction by polymer additives, well established for wall-bounded turbulent flows, is controversial in homogeneous, isotropic turbulence. To settle this controversy, we carry out a high-resolution direct numerical simulation of decaying, homogeneous, isotropic turbulence with polymer additives. Our study reveals clear manifestations of… (More)

We perform direct numerical simulations of the equations of magnetohydrodynamics with external random forcing and in the presence of gravity. The domain is divided into two parts: a lower layer where the forcing is helical and an upper layer where the helicity of the forcing is zero with a smooth transition in between. At early times, a large-scale helical… (More)

- Alfio Bonanno, Axel Brandenburg, Fabio Del Sordo, Dhrubaditya Mitra
- Physical review. E, Statistical, nonlinear, and…
- 2012

We study spontaneous breakdown of chiral symmetry during the nonlinear evolution of the Tayler instability. We start with an initial steady state of zero helicity. Within linearized perturbation calculations, helical perturbations of this initial state have the same growth rate for either sign of helicity. Direct numerical simulations (DNS) of the fully… (More)

- O . Löhmer, Melissa Kramer, T . Driebe, Axel Jessner, Dhrubaditya Mitra, Andrew G. Lyne
- 2004

We present results of high-precision timing measurements of the binary millisecond pulsar PSR J2145−0750. Combining 10 yrs of radio timing data obtained with the Effelsberg 100-m radio telescope and the Lovell 76-m radio telescope we measure a significant timing parallax of 2.0(6)mas placing the system at 500 pc distance to the solar system. The detected… (More)

We consider mean-field dynamo models with fluctuating α effect, both with and without largescale shear. The α effect is chosen to be Gaussian white noise with zero mean and a given covariance. In the presence of shear, we show analytically that (in infinitely large domains) the mean-squared magnetic field shows exponential growth. The growth rate of the… (More)

- Dhrubaditya Mitra, Jérémie Bec, Rahul Pandit, Uriel Frisch
- Physical review letters
- 2005

We study turbulence in the one-dimensional Burgers equation with a white-in-time, Gaussian random force that has a Fourier-space spectrum approximately 1/k, where k is the wave number. From very high-resolution numerical simulations, in the limit of vanishing viscosity, we find evidence for multiscaling of velocity structure functions which cannot be… (More)

- Prasad Perlekar, Samriddhi Sankar Ray, Dhrubaditya Mitra, Rahul Pandit
- Physical review letters
- 2011

We present a natural framework for studying the persistence problem in two-dimensional fluid turbulence by using the Okubo-Weiss parameter Λ to distinguish between vortical and extensional regions. We then use a direct numerical simulation of the two-dimensional, incompressible Navier-Stokes equation with Ekman friction to study probability distribution… (More)

- Faranggis Bagheri, Dhrubaditya Mitra, Prasad Perlekar, Luca Brandt
- Physical review. E, Statistical, nonlinear, and…
- 2012

We present direct numerical simulations of turbulent channel flow with passive Lagrangian polymers. To understand the polymer behavior we investigate the behavior of infinitesimal line elements and calculate the probability distribution function (PDF) of finite-time Lyapunov exponents and from them the corresponding Cramer's function for the channel flow.… (More)